Brazed Aluminum Heat Exchangers (BAHX)

Chart’s Brazed Aluminum Heat Exchangers (also known as a Plate Fin Heat Exchanger) and Cold Boxes are at the heart of low temperature natural gas, air separation and petrochemical processes worldwide.

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Chart Industries pioneered the use of BAHX for cryogenic gas processing in the 1950s and we’ve produced over 13,000 units since. A Chart BAHX is a highly efficient, all brazed and welded compact heat exchanger device that offers distinct advantages versus other heat exchanger types. They are designed in accordance with the world’s pressure vessel codes and deployed globally. Our principal design and manufacturing facility is in La Crosse, Wisconsin and notable Chart firsts include the introduction of vacuum brazing, Core-in-Kettle® and mercury tolerant construction.

Plate fin heat exchangers are essential for cryogenic gas processing applications worldwide including Air Separation, LNG liquefaction, Nitrogen Rejection, NGL Recovery, Propane Dehydrogenation and other low temperature natural gas and petrochemical processes.

The in-house designed and built BAHX are fundamental to Chart’s LNG liquefaction plants and complete integrated energy systems, including nitrogen rejection and propane dehydrogenation. In addition to stand-alone plate fin heat exchangers Chart offers fully assembled and tested battery assemblies and Cold Boxes.


Brazed Aluminum Heat Exchanger
BAHX Nomenclature

BAHX Footprint Comparison
BAHX Footprint vs. Shell and Tube Heat Exchanger

BAHX are at the center of these applications

Industrial Gas Production

  • Air Separation
  • Nitrogen Liquefaction
  • Helium Liquefaction
  • Argon Recovery

Petrochemical Processing

  • Amonia Purification
  • Ethylene
  • Hydrogen Recovery (HYCO)
  • Propane Dehydrogenation (PDH)

Natural Gas Processing

  • Nitrogen Rejection
  • Helium Recovery
  • Natural Gas Liquids (NGL) Recovery
  • Ethane Recovery

Liquid Natural Gas

  • Peak Shaving
  • Small & Mid-scale Liquefaction
  • Baseload
  • Floating LNG

Cold Box

Cold box Phases

Single plate fin heat exchangers can be supplied pedestal mounted and insulated locally in the field. However, and especially when the service requires multiple units assembled in series and/or parallel, a cold box is the most efficient solution.

Externally, a Cold Box is a carbon steel enclosure with flanged terminations to facilitate simple on-site connection to plant process pipework.

Cold Box Features

  • Provides inert atmosphere
  • Supports and houses
    • heat exchangers
    • piping
    • other related cryogenic equipment
    • insulation material
  • Modular assembly, includes instrumentation
  • Multiple services in a single piece of hardware
  • Complete, compact package

Chart’s primary Cold Box fabrication location is a 40-acre coastal facility in New Iberia, Louisiana, USA, providing direct access to the US inter-coastal waterway and the Gulf of Mexico.

Cold box manufacturing is supported by design and engineering from La Crosse, Wisconsin, and The Woodlands, Texas, USA.

Cold box


Chart’s patented Core-in-Kettle®, introduced in 1989, further extends the use of Brazed Aluminum Heat Exchanger technology in a range of petrochemical and natural gas processes as an alternative to traditional shell and tube kettle reboilers. Instead of a tube bundle, the external vessel houses one or more plate fin heat exchangers and provides around 10 times more heat transfer surface area and up to 20 times more ‘UA’ than the equivalent tube and shell unit.

The superior heat transfer performance can be utilized to produce a significantly more compact unit for new installations, or considerably more performance can be provided to existing installations by replacing the tube bundle with a Brazed Aluminum Heat Exchanger retro-fitted into the same shell. This is a particularly useful solution for process plant debottlenecking.

Plate fin heat exchanger construction permits close temperature approaches down to 2°F (1°C), resulting in significant power savings and reduced compressor horsepower.

How does Core-in-Kettle® work?

  1. The warm process stream fluid enters the Brazed Aluminum Heat Exchanger (BAHX) through steel inlet nozzle(s) on the vessel shell. The inlet nozzles are connected to the aluminum inlet pipes of the exchanger by an aluminum to stainless steel transition coupling.
  2. Inside the BAHX the warm stream cools as it flows against a cold stream.
  3. The cold stream enters the vessel either as a liquid or 2-phase fluid directly from a distillation column (or expansion valve in the case of a refrigerant).
  4. A liquid level is formed outside the BAHX core to create a liquid head that drives the cold stream liquid through the core
  5. A disengagement space above the core causes the liquid and vapour to separate.
  6. The cooled warm stream leaves the BAHX and vessel.
  7. The cold stream vapour exits the vessel through the outlet nozzles while the liquid falls back to be recirculated.
  8. A manway is provided in the vessel shell.

Core In Kettle

Support Services

Increased awareness, attention to operating data and process control will improve plant safety and reliability. Through Chart Lifecycle, we offer pro-active services intended to maintain the health and performance of your heat exchanger fleet to mitigate the risk of plant downtime and financial impact of lost production and revenue. Learn more at


BAHX Maintenance and Repair Services


  • Features
  • Literature

Features Include:

  • Custom engineered to meet customer’s thermal and hydraulic performance requirements
  • Proprietary in-house high performance simulation software results in optimal configurations
  • Comprehensive range of heat transfer fins and patterns, all proven to facilitate maximum design flexibility
  • A rigorous development program supports Chart’s commitment to continued improvements in thermal efficiency and high pressure design capability
  • Plate fin heat exchangers can be offered in accordance with all recognised applicable national design codes and Chart holds all major international quality accreditations